The main objective of this Program is to contribute to an understanding of the molecular mechanisms responsible for cancer by investigating fundamental genetic processes involved in the control of cell growth and exploring how these processes are perturbed in neoplastic and virus- transformed cells. The projects that make up the Program collectively address a number of general issues relevant to this objective. These include the replication of DNA tumor virus genomes, the regulation of cellular proliferation by growth factors and oncogenes, the control of the cell cycle, the regulation of gene expression in normal and neoplastic growth, the segregation of eukaryotic chromosomes during mitosis, and the integration of retrotransposons.